Edge currently does not support CSS 3 Text Decorations (only the spec as it was defined in CSS 2.1) so the behavior you are seeing is expected. We are constantly looking for ways to improve our product and have implementing further refinements of the spec on our backlog, though we don’t have any specifc plan to share as of right now. Feel free however to use our uservoice website and upvote/create a feature request. We only use this website to keep track of bugs, not feature requests.

Suggesting a root cause

Help make the web just work! Identifying a root cause helps us resolve issues more quickly. If you have a theory for the root cause or have identified and reduced a reproducible bug, include a description and any relevant code or URLs in your comment and mark it as a root cause suggestion. Our engineers will take a look and update the bug with the results of our investigation.